The fuel gauge stopped working suddenly, moored the boat one night it worked fine returned the next day and not functioning. Getting a reading with the ohm meter, 84.5 across the sending unit and the same at the instrument, 12v is present and have ground(the instrument light works). The gauge will read full if you short across S and G and also if you do the same at the tank. Actually replaced the gauge today and still no read with the new instrument. Took the old one below and hooked it to the sending unit and ran some 12v to it, hey it works8rzm I've got 3/4 tank. I'm guessing I have some type of ground issue and I'm not knowledgeable enough to know how to diagnose and repair.....
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Its an OHM meter not a volt meter
Most gages are just ohm meters with a fancy face. ALL tank sending units that I've ever seen (water, fuel.....) are variable resisters. If memory serves it is like 370 ohms to 72 ohms range full to empty. To test the sending unit just turn your multi meter to ohm and read across the terminals or between the one terminal and a good ground. You may need a helper to rock the boat to get the gage to change its reading or pull the gage and do it manually. If you read AT the sending unit you get a better indication of whether it is the problem. Then read across the terminals at the gage. If you have a "body grounded" type of sending unit with only one wire then the sending unit is using the ground circuit as the return path and that can be a pain tracking down. For body grounded types do your self a favor and clean the battery terminals. I know it should not make a difference in the resistance since it does not go through the battery but I've fix a few by wiggling the cables. It really helps business when you can "fix-um-at-the-pump for the little-old-lady-network
Most gages are just ohm meters with a fancy face. ALL tank sending units that I've ever seen (water, fuel.....) are variable resisters. If memory serves it is like 370 ohms to 72 ohms range full to empty. To test the sending unit just turn your multi meter to ohm and read across the terminals or between the one terminal and a good ground. You may need a helper to rock the boat to get the gage to change its reading or pull the gage and do it manually. If you read AT the sending unit you get a better indication of whether it is the problem. Then read across the terminals at the gage. If you have a "body grounded" type of sending unit with only one wire then the sending unit is using the ground circuit as the return path and that can be a pain tracking down. For body grounded types do your self a favor and clean the battery terminals. I know it should not make a difference in the resistance since it does not go through the battery but I've fix a few by wiggling the cables. It really helps business when you can "fix-um-at-the-pump for the little-old-lady-network
gauge
you probably have a ground problem buried in a harness somewhere. I had the same problem but it turned out to be the sending unit, but I also had a similar problem with an engine temp gauge. that turned out to be a bad ground, but I ran a separate ground and it worked.
you probably have a ground problem buried in a harness somewhere. I had the same problem but it turned out to be the sending unit, but I also had a similar problem with an engine temp gauge. that turned out to be a bad ground, but I ran a separate ground and it worked.
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